How to Write a Letter of Approval to a Student

We read among our applicants things like one of the best, a lot. It's a nice thing to say, but that's not all that helpful as we are trying to get to know individual applicants. Even if you say this is the best student I ever had, we want more than that. Was it just that she got high scores or can you give us some more specific examples here? Another great example would be someone saying something along the lines of Sophia is an incredible asset to the class.